Saturday, August 15, 2015

The law of superposition

The law of superposition poses a prima facie challenge to young-earth creationism. Here are two definitions:

His [Steno's] principle of superposition of strata states that in a sequence of strata, as originally laid down, any stratum is younger than the one on which it rests and older than the one that rests upon it.
Within a sequence of layers of sedimentary rock, the oldest layer is at the base and that the layers are progressively younger with ascending order in the sequence. This is termed the law of superposition and is one of the great general principles of geology.

All things being equal, the law of superposition is a reasonable, commonsense principle. It is, however, easy to come up with examples in which that principle can literally be turned upside down. 

For instance, suppose I dig a grave. After I'm finished, I have a pile of dirt. Because I was digging down, the layers are now in reverse order. What was originally the bottom-most layer is now the top-most layer. Each layer is now older than the one on which it rests and younger than the one that rests upon it. The layers are progressively younger in descending order. 

Archeology frequently excavates mounds. But what was the order in which layers were heaped on other layers? Does it represent layers of progressive occupation? Or is this the result of digging into the ground to reuse old materials? 


  1. Not being an archeologist, my first question would be: with the current state of the art, is it not possible to excavate in locations where you are relatively -- if not completely certain -- that the area has not been previously excavated; and, if so, and if such excavation confirms the law of superimposition, will this carry any weight with YECs?

    1. YECs field the law of superposition by appealing to two factors: (i) mature creation for bedrock; (ii) then a global flood (with seismic/tectonic activity and silt deposition) to relayer what's above. Whether that's scientifically adequate to account for the pattern is a separate question.

  2. That makes sense. Can you refresh my memory as to what is the most common OEC objection to mature creation? Is it the "God-as-deceiver" argument? The argument that God's physical laws were fixed? Or something else?

  3. It's also been demonstrated that multiple layers of sediment can be deposited simultaneously and laterally. There are examples of this happening, both in recent events (Mt. St. Helens) and in older strata (petrified trees positioned vertically that cross several strata). Of course, when multiple strata are deposited laterally, there is an angle to the line of deposit such that portions of upper strata are being deposited before portions of lower strata. For a vertical cross-section, it's obvious that the lower were deposited first, but at a cross-section greater than the angle of deposition, the upper strata will have been deposited first.